mail.casjay.pw has no CNAME records.
Question and response
Question
dig mail.casjay.pw. NS
Answer
The response has no answer records.
Authority
casjay.pw. 2740 SOA dns.casjay.pw. dns-admin.casjay.pw. 2026010172 10800 3600 1209600 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0